Electrical heating apparatus and method of making the same



y 1939. E. L. WIEGAND' 2,158,601

ELECTRICAL HEATING APPARATUS AND METHOD OF MAKING THE SAME Filed April 13, 1937 AT TO guz a v is to provide new and improved electrical heating I May 16,1939

"If UNITED v STATES PATENT orFica Wm HEATING APPARATUS IE'I'IIOD 0! KING THE SAME 29Ciaim.

My invention relates to electrical heating apparatus and method of making the same, and isv particularly adapted for embodiment in such apparatus oi the convection or forced convection type, and the principal object of my invention apparatus of these types and methods for making the same.

In the drawingaccompanying this speciflca tion, and forming part of this application, I have shown, for purposes of illustration, several forms which my invention may assume. In this drawing:

Figure 1 is a plan view of heating apparatus in my invention,

Figure 2 is asection taken along the line 2-2 of Figure 1, looking in the direction of the arrows,

Figure 3 is a fragmentary section taken along the line 8-4 of'Figure 2, looking in the direction of the arrows,

Figureiisadiagrammatlc viewofanaxial section of electrical heating apparatus, showing ,thatthersistoriUmaybeofanyothersuitable' one'wayin which electrical heating units such as shown 'in-Figure 1 may be utilized, and

Figures 5,- 6, and 7 are diagrammatic plan views of other embodiments of the invention.

Referring to Figural an electrical heating unit I. is here shown as comprising a general body portion ll provided with heat dissipating means l2. The general body portion ii is of oblong cross-sectional outline, as may be best seen in l'lgure2. Theprimarybodyportionisin the bisected within the sheet metal sheathof the strip heater II is aresistor I. which is here f show as a strip of electrical mistahee material,

the strip being of; undulating form and extending 'l ligitudinally within, the sheath one or more 'time'sas maybe desired. Itwillbeunderstood uform. "ilie resistor I0 is insulated from the sheath-byinsulation is disposed within the sheath andinwhichtheraistorisembedded. 'iheinla -desirably refractoryand in parthe form of an electrical heating unit embodying form ofan electric heater ll of the strip type,

terial, which, while electrically insulating, is heat conducting. 1

-' The heat dissipating means i2 here shown comprises fin means. The fin means may be of any suitable form In the illustrated embodiment l the fin means includes a plurality of fin elements 2i spaced longitudinally of the general body por- 7 tion H and extending transversely thereof. Each collar 22' is adapted to wedge into the recess or flare 22. If desired the end 24 may be slightly beveled to promote entrance of the end 24 into the recess or flare 23. 1

The fin elements 2 I ,are here shown as of oblong rectangular outline.

One end of the body portion of the strip heater II is here shown as provided with a pair of terminals 25, '28 connected within the sheath to the resistor is. I

In making such a heating unit llas shown in Figure 1 the primary body portion. constituted by the strip type heater It, may be first completed in the form of a rectilinear strip heater, this strip heater being entirely complete and comprising all of the constructional features hereinbefore pointed out with respect to the strip type heater II, with the exception that the body portion is rectilinear. The finned elements constituted by the collars 22 and fin elements 2| may be then telescoped over .the strip heater, and, desirably, enough finned elements are telescoped onto the strip heater so that substantially of the heater is occupied by a the entire length finned elements. The last, or both the first and last finned element telescoped onto the heater may, if desired, be brazed to the sheath of the heater, or otherwise suitably fastened thereto; At this stage of. the process the heating unit comprises a strip heater provided with heat dissi-' pating means, and the general locus'of the heating unit, as determined by the strip heater. is rec: tilinear. The heating-unit is then bent to the form shown in Figure 1 in which, as shown. the unit ll forms approximately a complete I have found that thejrectilinear 'flnned strip heater may be brought to the form. shown in Figure 1, by holding the finned strip heater at its ends and bending it around some round object, with'its wider side against the a is of such l0 round object. Another way is to place the finned strip heater between templates or Jigs and press it into shape. Pads may be used on the templates in the form of a'rubber coating, for exampie, to keep the fins from skidding and being bent out of proper spacing. Still another way is to pass the finned strip through bending rolls which may be covered with a padding such as rubber. On the other hand, the unit may also be produced by first bending a strip heater to the desired form and then applying the fin means thereto.

The unit may be bent to other non-rectilinear forms, as for example in the form of a spiral, as shown in Figure '7, or to other forms not necessarily arcuate. In instances where it may become undesirable to provide a single unit, such as shown in Figure 1, by reason of the undue length of the circumference of a circle which it is desired to have occupied by heating means, two units Illa, 10b may be utilized, as shown in Figure 5, each of which is bent to the form of an approximate semi-circle. This form also has the advantage of reducing the amount of current which must be carried by the terminals of a given unit. In Figure 5 the terminal ends or the two units are shown as disposed adjacent each other so that they may be readily connected respectively to a single pair of lead-in conductors from a source of current (not shown).

In Figure 6 three arcuate units We, Mid, its, are shown, these units being so formed that together they approximately define a complete circle. The embodiment of Figure 6 maybe advantageously used in connection with a three phase source of current (not shown), each one of the units 'beingconnected across a diii'erent phase of the three phase supply.

Obviously, any number of heating units may be used to complete a circle or define any other desired configuration.

Heating units in accordance with my invention are particularly adapted for use in heating apparatus of the air blast type or in general for forced circulation of fluid. One particular such embodiment is diagrammatically illustrated in Figure 4.

In the apparatus shown in Figure 4 there are three tiers A, B, C, of heating units, disposed in the same general plane, and each of these tiers may comprise a single substantially circular heating unit such as shown in Figure l, or several heating units, such as shown in Figures 5 and 6. Two more sets of tiers A B C and A, B, C are shown in Figure 4 and each tier 01 each of these sets may be constructed and arranged similarly to the first set of tiers. It will be obvious that where there are three sets of tiers with three tiers in each set that the heating units may be most readily connected to a three phase source of current and the load on the three phases balanced. It will of course be understood that the arrangement shown in Fisure 4 is merely illustrative, and that the number of units may range from one only to any desired number and any suitable arrangement; and that the source of supply may be alternating current single phase, two phase, three phase, or any other suitable supply of current, with any suitable control means, thermostats, safety cut outs (not shown) as desired and as will be understood by those skilled in the art.

In Figure 4 the heating units are shown as disposed around and concentric with a cylindrical wall 21, and at the right hand end of the wall 21, as viewed in Figure 4, there is provided a baille 28 which may be of conical form. Surrounding the outer periphery of the sets of tiers of units is a generally cylindrical housing 28, and within the right hand frustro-conical end 30 of this housing there is disposed a fan 3|, driven by a motor 31, for blowing air through the annular passage provided by the cylindrical wall 21 and by the generally cylindrical housing 29. The stream of air directed against the heating units disposed in the annular passage meets the narrow edge of the general body portion of any given unit and passes axially along the wider side of the body portion and between the fin elements, thestream continuing to the next axially adjacent heating units, and so on depending upon the number of heating units disposed axially adjacent to each other.

If desired, the cylindrical housing 29 may have disposed thereabout a jacket including a generally cylindrical wall 32, the left. hand end 33 of which is spaced from a flange 34 which may be provided on the cylindrical housing 29, to provide an inlet passage 35. The right hand end ll of the outer cylindrical wall 32 may be spaced from the wall 30 and formed in any suitable way to house the right hand side of the Ian 3i, and

may be so constructed that the fan motor 31 is outside of the end wall 38 or thejacket. Thus, a passage 39 is provided so that air may enter the inlet 36 and proceed through this passage to the inlet side of the fan 31 and through the tan be directed through the annular passage between the cylindrical wall 21- and the cylin drical housing 29. By passing the air, before it reaches the Ian, throughthe passage 39, the air is pre-heated and at the same time serves as an insulating jacket for the housing 29.

From the foregoing it will be apparent to those skilled in theart that each of the illustrated embodiments of my invention provides a new and improved electrical heating apparatus, readily and conveniently constructed and assembled, and accordingly, each accomplishes the principal object of my invention. On the other hand, it also will be obvious to those skilled in the art that the illustrated embodiments of my invention may be variously changed and modified, or features thereof, singly or collectively, embodied in other combinations than those illustrated, without departing from the spirit of my invention, or sacrificing all of the advantages thereof, and that accordingly, the disclosure herein is illustrative only, and my invention is not limited thereto.

i claim: 5

1. An electrical heating unit having a body havlug at least a portion the general longitudinal locus of which is non-rectilinear; said body portion including a resistor, a metallic sheath for said resistor, and means for insulating said resistor from said sheath; and heat dissipating means on said portion, including a plurality of annular members disposed axially adjacent each other about said portion, said annular members being respectively provided with a transversely extending flange.

2. An electrical heating unit having a body having at least a portion the general longitudinal locus of which is non-rectilinear; said body including a heating element comprising a. resistor,

a sheet metal sheath for said resistor, and means for insulating said resistor from said sheath; and

' a plurality of annular members disposed axially adjacent each other about said portion, said an- 'nular members being respectively provided with a tramve rsely extending fiange.

3. The process 01' making an electrical heating unit which comprises: successively telescoping onto an elongatedelectrical heating element having a body including a sheet metal sheath the general longitudinal locus oi which is substantially rectilinear, a plurality of annular members each provided with a transversely extending flange to form a. finned heating element assembly and then bending at least a portion of said assembly so that the general longitudinal locus of said portion is non-rectilinear.

4. An electrical heating unit having a body having at least a portion the general longitudinal locus oi which is nonerectilinear; said body portion including a heating element comprising a resistor, a metallic sheath for said resistor, and means for insulating said resistor from said sheath; and heat dissipating means on said body Portion, including longitudinally spaced sheet metal fin means having elements 01 cross-section each defining a dihedral angle having a first leg in contact with said body portion and a second leg extending transversely to said first leg at one margin or said first leg so that said second legs of said elements extend transversely of and away from said body portion and are spaced by said first legs.

-5. An electrical heating unit having a body having at least a portion the general longitudinal locus oi which is non-rectilinear; said body portion including a resistor embedded in compacted granular refractory insulating material, and a sheet metal sheath for said insulating materal; and heat dissipating means on said sheath, including longitudinally spaced sheet metal finmeans having elements of cross-section each defining a dihedral angle having a first leg in con- I tact with said sheath and a second leg extending transversely to said first leg at one margin oi said first leg so that said second legs of said elements extend transversely of and away from said sheath and are spaced by said first legs.

6. In combination: a plurality of electrical heating units each having at least a portion the general longitudinal locus of which is non-rectilinear; said portion including a resistor, a metallic sheath for said resistor, and means for insulating said resistor from said sheath; means 'for directing a stream of fluid against said units; at least one of said units being disposed in a first general plane transverse to the general direction of said stream of fiuid, and at least one other of said units being disposed in a second general plane spaced from said first plane and also transverse to said stream oi fiuid; each of said units having heat dissipating means forming a part-thereof and disposed on said portions of the respective units and comprislng fin means extending transversely of said respective portions.

7. In combination: at least two electrical heatlng units the general longitudinal locus of each of which is substantially circular and of substantially the same diameter; each of said units in-- uding a resistor; a metallic sheath for said reslstor, and means for insulating said resistor from said sheath; means for directing a stream 01' fiuid a ainst said units; at least one of said units being i disposed in a first general plane transverse to the general direction oi said stream 01' fiuid, and at least one other of said units being disposed in a second general plane spaced from" said first plane and also transverse to said stream oi fiuid; each of said units having heat disnpating means form. ing a part thereof and comprising fin means ex tending transversely of said respective units.

8. In combination: a plurality of electrical heating units the general longitudinal locus of the major portion of each of which is arcuate, said units being disposed in the same general plane with said locuses defining a circle; each of said major portions including. a resistor, a metallic sheath for said resistor, and means for insulating said resistor from said sheath; means for direct ing a stream of fluid against said units in a direction transversely of said plane; each of said units having heat dissipating means forming a unitary part thereof and disposed on said portions oi the respective units and comprising fin means extending transversely of said respective portions.

9. The process of making an electrical heating unit which comprises: providing an elongated electrical heating element including a sheet metal sheath the general longitudinal locus of which is substantially rectilinear, with heat dissipating means including longitudinally spaced fin means by applying to said sheath sheet metal means having elements of cross-section defininga dihedral angle having a first leg and a second leg extending transversely to said first leg at one margin of said first leg, so that the first legs of sheath andare spaced by said first legs, and then bending at least a portion of said assembled heat that the general longitudinal locus of said portion is non-rectilinear.

10. The process of making an electrical heating unit which comprises: providing an elongated electrical heating element including a sheet metal sheath the general longitudinal locus of which is substantially rectilinear, with heat dissipating means including longitudinally spaced fin means by applying to said sheath sheet metal means having elements of cross-section defining a dihedral angle having a first'leg and a second leg extending transversely to said first leg at one margin of said first leg so that thefirst legs of said elements lie against said sheath and said second legs extend laterally awayirom said sheath and are spaced by said first legs, and then bending said assembled heat dissipating means and said heating element so that the general longitudinal locus of the major portion of said unit is arcuate.

11. An electrical heating unit having a body having at least a portion the general longitudinal locus of which is arcuate; said portion including a resistor, a metallic sheath for said resistor, and

\ cluding a resistor embedded in compacted granular refractory insulating material, a sheet metal sheath for said insulating material; and heat disv ill sipating means on said portion, including a plurality o! annular members disposed axially ad- .,iacent each other aboutsaid sheath at said por- ,0. said elements lie against said sheath and said second legs extend laterally away from said tion, said annular members being respectively provided with a transversely extending flange.

13. In combination: a plurality of electrical heating units the general longitudinal locus of at least a portion of each which is arcuate, said units being disposed with said arcuate locuses substantially concentric; each of said portions spectlve portions.

iii)

i l. In combination: an electrical heating unit having a body having at least a portion. the general longitudinal locus of which is non-rac tilinear, said body portion having an oblong crosssectional outline the longer axis of which is transverse to the general plane of said locus; said body portion comprising a resistor, a metallic sheath for said resistor, and means for insulating said. resistor from said sheath; heat dissipating means mounted on said portion and forming a unitary part of said portion and extending transversely of the longitudinal locus of said portion; and

means for directing a stream of air against said unit edgewise of said body portion.

15. An electrical heating unit having a body having at least a portion the general longitudinal locus of which is non-rectilinear; said body portion including a resistor, a metallic sheath for said resistor, and means for insulating said resistor from said sheath, said body portion having an oblong cross-sectional outline-the longer axis of which is transverse to the general plane of said locus; and heat dissipating means on said body portion, including longitudinally spaced sheet-metal fin means having elements of crosssection each defining a dihedral angle having a first leg in contact with said body portion and a second leg extending transversely to said flrst leg at one margin of said first leg so that said second legs of said elements extend transversely of and away from said body portion and are spaced by said first legs.

16. The process of making an electrical heating unit which comprises: successively telescoping a plurality of annular members, each provided with a transversely extending flange, onto an elongated electrical heating'element having a body portion the general locus of which is substantially rectilinear, said body portion including a heating elernent comprising a resistor, a metallic sheath for said resistor, and means, including refractory ma terial, constructed and arranged to insulate said resistor from said sheath, to form a finned heating element assembly, and then bending at least a portion of said assembly so that the general longitudinal locus of said portion is non-recti linear.

17. The process of making an electrical heat ing unit which comprises: providing an elongat ed electrical heating element including a sheetmetal sheath the general longitudinal locus of which is substantially rectilinear and the crosssectional outline of which is oblong, with dissipating e a n s including longitudlnaliy spaced fin means by applying, to said sheath,

sheetmetal means having elements of cross-section defining a dihedral angle having a firstleg and a second leg extending transversely to said first leg at one margin of said first leg, so that the first legs of said elements lie against said sheath and said second legs extend laterally away from said sheath and are spaced by said first legs, and then bending at least a portion of said assembled heat dissipating means and saidheating element so that the general longitudinal locus of said portion is non-rectilinear and the general plane of the non-rectilinear locus is transverse to the longer axis of .said oblong crosssectional outline.

18. The process of making an electrical heating unit which comprises: providing an elongated electrical heating element including a sheetmetal sheath the general longitudinal locus of which is substantially rectilinear and the crosssectional outline of which is oblong, with heat dissipating means including longitudinally spaced fin means by applying, to said sheath, sheetmetal means having elements of cross-section defining a dihedral angle having a first leg and a second leg extending transversely to said first leg at one margin of said first leg so that the first legs of said elements lie against said sheath and said second legs extend laterally away from said sheath and are spaced by said first legs, and then bending said assembled heat dissipating means and said heating element so that the general longitudinal locus of the major portion of said unit is arcuate and the general plane of said arcuate locus is transverse to the longer axis of said oblong cross-sectional outline.

19. An electrical heating unit having a body having at least a portion the general longitudinal locus of which is non-rectilinear; said body portion including a heating element comprising a resistor, a sheet-metal sheath for said resistor, and means for insulating said resistor from said sheath, said insulating means including compacted granular refractory material; and heat dissipating means on said portion, including a plurality of annular members disposed axially adjacent each other about said portion, said annular members being respectively provided with a transversely extending flange.

20. An electrical heating unit having a body having at least a portion the general longitudinal locus oi which is non-rectilinear, said body portion having an oblong cross-sectional outline the longer axis of which is transverse to the general plane of said non-rectilinear locus; said body including a resistor embedded in compacted granular refractory insulating material, a sheet.- metal sheath for said insulating material; and heat dissipating means on said portion, including a plurality of annular members disposed axially adjacent each other about said sheath at said portion, said annular members being respectively provided with a transversely extending flange. 21. An electrical heating unit having a body having at least a portion the general longitudinal locus or which is non-rectilinear; said body por-.

tion including a resistor embedded in compacted granular refractory insulating material, and a sheet-metal sheath for said insulating material, said body portion having an oblong cross-sectional outline the longer axis of which is trans verse to the general plane of said locus; and heat dissipating means on said sheath, including longitudinally spaced sheet-metal fin means having elements of cross-section each defining a dihedral angle having a first leg in contact with said bending at least a portion 'heatdissipatingmeansandsaid portions surrounding sheath and aseccnd leg mendin transversely at me margin of said first le sothatsaidsecondlegsoisaidelements extend transversclyotand awaytromsaid sheath and are spaced by said first legs.

22.'lhe processoimakinganelectricalheating unit which comprises: providing an elongate electrical heating element the general longitudinal locus or which is substantially rectilinear, with heat dissipatim means including longitudinaliy spaced fin means transversely of the longitudinal locus of said heating element. said heat ingmeansandsaidheating elementsothat the general longitudinal locus oi said portion is nonrectilinear. 1

ing unit which comprises: gated electrical heating element the general longitudinal locus of which is substantially rectilinear, with heat dissipating means including means extending oi the longitudinal locus of said fin portions telescopically of said assembled heating element so that the general longitudinal locus of said portion is non-rectilinear.

of making an electrical heatcomprises: providing an elongated electrical heating element having an oblong cross-sectional outline and having a general longitudinal locus which is substantially rectilinear, with heat dissipating means including longitudinally spaced fin means extending transversely of the longitudinal locus of said means including portions integral with said fin means for spacing said fin means longitudinally, and then bending at least a portion of said led heat dissipating'means and said heating element so that the general longitudinal locus of said portion is non-rectilinear and the general plane of said non-rectilinear locus is transverse to the larger axis of said oblong cross-sectional out- 25. The process of making an electrical heating unit which comprises: providing an elongated electrical heating element having an oblong cross-sectional outline and having a general longitudinal locus which is substantially rectilinear, with heat disipating means including longitudinally spaced fin means extending transoi said heating with said fin means for spacing said fin means longitudinally, wedgin said spacing portions telescopically into each other, and then bending at least a portion of said assembled heat dissipating means and said heating element so that the general longitudinai'iocus of said portion is non-rectilinear and the general plane 01 said cross-sectional outline the sipating non-rectilinear locus is transverse to the longer axis of said oblong cross-sectional outline.

26. In combination: an electrical heating unit having a body having at least a portion the general longitudinal locus or which is nonrectilinear, said body portion having an oblong longer axis of which is transverse to the general plane of said locus; said body portion including a resistor, a metallic sheath for said resistor, and means for insulating said resistor from said sheath; and heat dissipating means mounted on said portion and forming a unitary part of said portion and including fin means extending transversely of the longitudinal locus 0! said portion.

27. In combination: an electrical heating unit having a body having at least a portion the general longitudinal locus of which is non-rectilinear; said body portion including a resistor, a metallic sheath for said resistor, and means for insulating said resistor from said sheath; heat dissipating means mounted on said body portion and forming a unitary part of said portion and including longitudinally spaced fin means extending transversely of the longitudinal locus of said portion; and said'heat dissipating means including portions surrounding said body portion and integral with said fin means so constructed and arranged as to space said fin means longitudinally, said spacing portions being so constructed and arranged that they are telescopically wedged into each other.

'28. In combination: an electrical heating unit having a body having at least a portion the general longitudinal locus or which is non-rectilinear. said body portion having an oblong crosssectionaloutline and including a resistor, a. metallic sheath for said resistor. and means for insulating said resistor from said sheath; heat dissipating means mounted on said body portion and forming a unitary part 0! said portion and including longitudinally spaced fin means extending transversely of the longitudinal locus of said portion; including portions tion and integral with said fin means so constructed and arranged as to space said fin means longitudinally, said spacing portions being so constructed and arranged that they are telescopically wedged into each other.

29. In combination: an electrical heating unit having a body having at least a portion the general longitudinal locus or which is non-rectilinear, said body portion having an oblong cross-sectional outline the longer axis of which is transverse to the general plane 0! said locus; said body portion including. a resistor, a metallic sheath for said resistor, and means for insulating said resistor from said sheath; heat dismeans mounted on said portion and forming a unitary part of said body portion and including longitudinally spaced fin means extending transversely of the longitudinal locus of said portion; and said heat dissipating means including portions surrounding said body portion and integral with said fin means for spacing said fin means longitudinally, said spacing portions being so constructed and arranged that they are telescopically wedged into each other.

- EDWIN L. WIEGAND.

and said heat dissipating means surrounding said body por- 

